Detailed Description

This is a field type class. HDate holds a date value, which is a date type in the sql database too. (varchar in sqlite, but handled with functions) The HDate can hold a valid date or an unknown date. You can set the HDate to accept unknown date value or not. If you set the accesibility of unknown value with possible_unknown() the value can be unknow, (NULL in database). You can disable the accesibiliy of unknown value with impossible_unknown()
The default value can be:

A valid date (as known)

"NOW" the currend date (as known)

"UNKNOWN" an unknown value (if you set to known the date will be 2000-01-01)

"UNKNOWN_AND_NOW" an unknown value (if you set to known the date will be current date)

Gui appearance: A date editor widget and a checkbox if the unknown value is accepted (QDateEdit & QCheck)

Returns string format of the field's value. Very similar to getSQLValue() but the result is always acceptable in an sql varchar field. (Mostly used by the logger system, when every kind of values are stored in varchar. The gsafe try to keep the value as close to the original sql database value as possible)